AY Honors/Physics/Answer Key

1. Define the following:

a. Physics

A branch of science that deals with matter, energy, motion, charge, and force.

Physics uses a number of tools such as a balance, meter or ruler, clock or stop watch. Physicist also use more complicated tools as they look at more complicated events. The most important tool of physics is mathematics. You can think of Mathematis as the language of physics.

b. Mass

A quantity of matter related to weight by Newton's second law of motion represented mathematically as [math]\displaystyle{ F=m \times A }[/math]

c. Work

A measure of energy. If we push a heavy load, then the work that we do is how hard we push the load times how far we push the load.

[math]\displaystyle{ Work=Force \times distance }[/math]

d. Force

An influence on an object that causes the object to move or change direction.

e. Power

How much energy expended per unit of time. If you can do lots of work quickly, then you are using more power.

[math]\displaystyle{ Power= \frac{(Work\ done)}{(time\ it\ took\ to\ do\ the\ work)} }[/math]

f. Potential energy

The energy of an object based on its relation to other objects. For example if I lift a ball above the ground by a given distance, then the ball has the potential to fall the distance that I've raised it. The potential energy of a ball can be measured by measuring how high you raise the ball against the force of gravity on the mass of the ball.

Potential energy of the ball (E) = Mass of ball (m) * Accelleration of gravity (g) * height we rase the ball (h)

We write this [math]\displaystyle{ E=mgh }[/math]

g is the acceleration of gravity and is 9.8 m/sec/sec or 32 feet/sec/sec

g. Kinetic energy

The amount of energy that an object has based on its motion relative to other objects. Kinetic energy in it's simplest form is related to the speed of an object in relation to the observer. Kinetic energy in it's most complex form can be heat

The kinetic energy of a moving ball can be measured by knowing 2 things about the object 1) The mass of the object. (Determined using a scale.) 2) The velocity of the object (Time how long it takes to travel a given distance)

[math]\displaystyle{ Kinetic\ energy = 0.5 \times (Mass\ of\ object) \times (Velocity\ of\ object)^2 }[/math]

h. Weight

The force that gravity exerts upon a body. According to Newtons second Law of motion:

[math]\displaystyle{ The\ weight = (mass\ of\ object) \times (local\ acceleration\ of\ gravity) }[/math]

Weight is commonly mistaken for mass, but weight could be significantly more on a planet with larger gravity, or could be significantly less on a planet with a lower gravity. Mass on the other hand is the same in both circomstances.

i. Matter

Something that has mass. There are four states of matter: solid, liquid, gas, and plasma.

j. Inertia

A property of matter that works against an external force. According to Newton's first law of motion, a body at rest tends to stay at rest unless acted on by an outside force. An object in motion tends to stay in motion unless acted on by a force.

References

--Rodneyeast 14:06, 23 October 2006 (UTC)